The present invention relates to a process for using an SiH-olefin platinum catalyzed composition for insulating components from fire and more particularly the present invention relates to a process for utilizing an SiH-olefin platinum catalyzed composition for insulating electrical components in a nuclear plant from fire so as to maintain the electrical integrity of the electrical components that are insulated.
The SiH-olefin platinum catalyzed compositions are well known, such compositions broadly comprising a vinyl-terminated polysiloxane polymer having a viscosity of anywhere from 100 to 500,000 centipoise at 25.degree. C. The viscosity of the polymer can also be in the neighborhood of from 1,000,000 to 300,000,000 centipoise at 25.degree. C. However, for the purposes of the present invention only vinyl-containing polymers are considered which have a viscosity below 1,000,000 centipoise at 25.degree. C. Such vinyl-containing polydiorganosiloxane polymer which is preferably vinyl-terminated is taken and mixed with the desired amount of silica filler, usually from 10 to 200 parts of silica filler. As the cross-linking agent there is utilized a hydrogen-containing silicone resin or hydrogen-containing polysiloxane polymer. Finally, there is present in the composition anywhere from 1 to 200 parts per million of platinum in the form of a solubilized platinum complex catalyst.
A preferred form of solubilized platinum complex catalyst is platinum complexed with ether, an aldehyde or aliphatic alcohol. Another preferred type of platinum complex catalyst is platinum complexed with a vinyl-containing polysiloxane in which the chlorine content is such that the chlorine content does not exceed 1 gram atom of chlorine per gram atom of platinum. In such a composition there may be incorporated other additives such as low viscosity vinyl-containing fluids.
In any case the vinyl-containing base polymer, along with the silica filler and preferably with a platinum catalyst is packaged separately. The hydrogen polysiloxane with some of the vinyl-containing base polymer or by itself is also packaged separately. When it is desired to cure the composition, the two packages or two components are mixed, the composition is applied to the desired form and allowed to cure at room temperature to a silicone elastomer over a period of time varying anywhere from a few minutes to 24 hrs. As is known well-known inhibitors may be incorporated into such a composition such as, hydroperoxy compounds, acetylenic compounds and vinyl-containing cyclotetrasiloxanes to give the composition extended work life at room temperatures. Such compositions are also known where the base vinyl-containing polymer and optionally the hydropolysiloxanes have fluorinated substituent groups. For instance such compositions can be found in the disclosure of Jeram, U.S. Pat. No. 4,041,010, entitled "Solvent Resistant Room Temperature Vulcanizable Silicone Rubber Compositions", whose disclosure is hereby incorporated by reference. Such compositions having silicone elastomers formed therefrom have many uses, for instance, as electrical potting compounds, for forming molds for the fabrication of various plastic parts as paper release coatings, etc.
Irrespective of these many prior uses, in recent times there has risen the proliferation of nuclear power plants as utilities for the supplying of electrical energy and power to industry and private homes. In such nuclear power plants, the most predominate concern is the nuclear reactor itself, and to see that the nuclear reaction is carried out in a safe manner. However, precautions have also to be taken as far as any other extingiencies are concerned as, for instance, the possibility of fire. The possibility of fire in a nuclear plant is of even more concern than in the normal plant. In a nuclear plant even with many of the present safeguards there is possibility of an uncontrolled and unchecked fire spreading through a nuclear plant with wide-spread damage occurring. Although there are many safeguards against this possibility built into nuclear plants there is continuous effort made in further insuring the maintaining of the nuclear reactor's operation in as safe a manner as possible even with the possibility of an unchecked fire occuring in the nuclear plant. Accordingly, in connection with such concern, there has been constant effort applied in insulating electrical components and electrical cables from fire as much as is humanly possible so as to prevent fire from burning and destroying the electrical integrity of such electrical components and electrical cables, thus causing serious malfunction of the nuclear power plant and possibly even of the nuclear reactor itself. To insulate such electrical components or electrical cables from fire there have been utilized many types of procedures including the encasing of electrical components in concrete or other masonry material. However, the difficulty with such insulative techniques is that it is difficult to repair or replace the electrical component if it should break down or a design change be made.
Accordingly, it is highly desirable to have an insulative material for such electrical components in nuclear plants which will insulate the electrical component or cable as much as possible from fire, yet can be removed without great effort to repair or replace the electrical component. One effort in this direction has been the formulation of burn resistant silicone foam compositions. One example of a fire retardant silicone foam which can be used for this application is, for instance, to be found in the disclosure of Schuyler B. Smith, U.S. Pat. No. 3,923,705, which disclosure is hereby incorporated by reference. Such a foam is formed by reacting a silanol-containing diorganopolysiloxane polymer with a hydrogen-containing polysiloxane polymer in the presence of platinum catalysts such as are disclosed in the reference. It is also disclosed that additional flame retardant additives can be added to the composition such as carbon black.
A disclosure which relates to a silicone foam having burn resistant properties which is as useful as an insulative material for electrical components in nuclear plants is the disclosure of Frank J. Modic, Ser. No. 886,186 now U.S. Pat. No. 4,189,545, entitled "Silicone Foam Composition which has Burn Resistant Properties" and which was filed on the same date as the instant disclosure. This disclosure which is incorporated in the present case by reference discloses a foam formed by reacting a vinyl-containing polysiloxane with a hydrogen-containing polysiloxane in the presence of a platinum catalyst with the preferred platinum catalyst being the reaction product of a platinum halide reacted with a vinyl-containing polysiloxane in which the gram atoms of chlorine to gram atoms of platinum does not exceed one. Such a composition includes also as a necessary ingredient small amounts of water which act as the blowing agent for allowing the foam to form.
Such burn resistant silicone foams are desirable as insulative materials for electrical components in nuclear plants. However, they have two main disadvantages in that they are not as burn resistant as would be desired. Another disadvantage of such silicone foams is that they act as heat insulators and thus do not conduct the heat generated by the electric current away from the electrical copper cables very efficiently. Accordingly, the electrical components and specifically electrical cables which are insulated may at times overheat due to the good insulative properties of the foam and as such not conduct as much of the electrical current in an electrically efficient manner as would be desired. This may result in the use of oversized electrical components and electrical cables to overcome the deficiency of the silicone foams in this respect. Accordingly, while the burn resistant properties of the silicone foams are acceptable and specifically that of the Modic application is acceptable, nevertheless, it is highly desirable to find a silicone composition with even better burn resistant properties.
It should be noted that the silicone foams have one advantage that is not matched by other silicone compositions in terms of acting as burn resistant insulative materials for electrical components, that is, due to their presence as a foam they are cheaper than other silicone compositions to be used as burn resistant properties. Also, in high rise buildings having electrical components in conduits and other segregated areas as it is also essential to protect and insulate from fire such electrical components with a composition or other means so that the electrical components will maintain their integrity as long as possible; for instance, the electrical circuitry operating the elevators in high rise buildings.
It is also desirable in many ship constructions to insulate all electrical components, steam lines and other components from fire as long as possible. There has been utilized for this purpose, asbestos boards. However, the difficulty with such material even though they are good fire insulative materials is that it is difficult many times to fit the insulative material properly about the component or unit to be insulated from fire.
Accordingly, it was highly desirable to have a pourable composition which would easily fill the spaces and cavities around the electrical component and cure to form a solid which could then insulate the electrical component or other unit as long as possible from fire and maintain its integrity.
Accordingly, it is one object of the present invention to provide a process for insulating electrical components in nuclear plants, ships and high rise buildings which are located in segregated areas or conduits by the use of an SiH-olefin platinum catalyzed composition. It is an additional object of the present invention to provide a process for insulating electrical components in conduits in nuclear plants by using solid SiH-olefin platinum catalyzed compositions so as to result in an insulative electrical component with optimum burn resistant properties.
It is an additional object of the present invention to provide for a process for insulating electrical components in a conduit from fire in a nuclear plant in which the heat generated by the electric current is dissipated at a high rate such that the electrical component or electrical cable does not heat up and maintains its electrical integrity with slight, if any, loss of its efficiency.
Still an additional object of the present invention is to provide for a process in which a pourable SiH-olefin silicone rubber composition is utilized to fill the cavities around an electrical component in a conduit in a nuclear plant such that the insulated and enclosed electrical component conduits the heat away that is generated in the electric component.
These and other objects of the present invention are accomplished by means of the disclosure set forth hereinbelow.